I might be at a bit of a loss regarding the mounting / orientation of this antenna.
The manual's exact wording is "the antenna usually works best when mounted horizontally"

So I am taking the word "mounted" and thinking "side of the house" with the panel facing out, flat side pointed in the direction I am concentrating on.

But when I look at some pictures, it may appear that the antenna itself almost seems to be angled horizontally (like a floating plate) rather than vertically which is the way I picture a panel antenna operating.

Regardless, each position offers unique reception capabilities, but in practice does anyone know what the actual correct orientation is, as there is also an adjustment to rotate the panel left or right by a few degrees.

Looking at the RCA website, it shows the antenna mounted vertically on the side of a house. I suspect that's the optimal way for reception, but you can experiment and see if you get any other interesting results.

I have seen this antenna, used other RCA outdoor and indoor antennas but have not used this one. Please post your reception quality as I would be interested. Do you know if it covers low VHF, as well as high VHF and UHF?

Sorry I couldn't be of more help TickingMind, but your post caught my eye. See below for link to website. Thanks.

Kind of a weird way of doing things but I put a wireless webcam in front of the TV with the signal menu displayed, up onto the roof with my cellphone to view the screen.
Indeed it would seem the panel should not be positioned like a plate (up & down), rather pointed in the direction of the broadcast origin as suggested (Thanks!!)

I had tried a multibay adjustable antenna, one panel facing towards Toronto and the other facing towards Buffalo. While it did work, the antenna would often have a channel present one day and then the next it would no longer exist. We do have a very powerful antenna (CHCH and another one) which is line of site, visible from my roof, which I feel may be causing distortion, so the wide angel panel with a less aggressive gain seemed more feasible. At this point I have it situated more towards the north point towards Toronto, trying to gauge how it performs before I swing it south a bit to start picking up the US stations. When I hit that sweet spot, if any, I will report my findings.
Cheers,
TM

Seeing I had a reflector from a Channel Master 4 Bay, I rigged up a way to mount the ANT800 panel in front of it, 6 inch spacing. This improved reception (more directional, but solid), which permitted me to receive more stations in one area, but cutting some off to the side. If the solution withstands a few days and continues to give solid reception, looks like I've added 4 more channels on the Toronto side of things, I will do a duplicate setup for the southerly transmitters (Buffalo) and see how that works out.

Seeing I had a reflector from a Channel Master 4 Bay, I rigged up a way to mount the ANT800 panel in front of it, 6 inch spacing. This improved reception (more directional, but solid), which permitted me to receive more stations in one area, but cutting some off to the side. If the solution withstands a few days and continues to give solid reception, looks like I've added 4 more channels on the Toronto side of things, I will do a duplicate setup for the southerly transmitters (Buffalo) and see how that works out.

Do you think you could show and tell with a pick.
Sounds good well have a good day!!!